Final answer:
LCL, PTCHY, and XTNSV are terms from a Graphical Forecast for Aviation indicating local, patchy, and extensive weather phenomena, which are essential for pilots and flight planning.
Step-by-step explanation:
The abbreviations LCL, PTCHY, and XTNSV are used in a Graphical Forecast for Aviation (GFA) to describe weather conditions relevant to aviation. 'LCL' stands for Local, indicating weather phenomena that are not widespread but occur in small, specific areas. 'PTCHY' refers to Patchy conditions, suggesting that the weather phenomena are scattered or irregularly distributed across an area. Lastly, 'XTNSV' means Extensive, indicating that the weather phenomena cover a large area. These terms are crucial for pilots and flight planners to understand the scope and impact of weather on their intended flight paths.